The present invention relates to a substrate processing apparatus for performing various kinds of processing for a substrate such as a semiconductor wafer or the like, for example, a substrate processing apparatus for coating the substrate with a resist and developing the exposed substrate.
In the process of fabricating a semiconductor device, there is a series of processing steps of coating a semiconductor wafer which is a substrate to be processed with a photoresist solution, reducing a circuit pattern or the like and exposing a photoresist film by means of photolithography, and performing developing processing. These processing steps are extremely important to high integration of the semiconductor device.
In these processing steps, the semiconductor wafer which has undergone cleaning processing is first subjected to hydrophobic processing in an adhesion processing unit and cooled in a cooling processing unit, and thereafter a photoresist film is formed by coating in a resist coating unit. The semiconductor wafer on which the photoresist film is formed is subjected to pre-bake processing in a hot plate unit, cooled in a cooling processing unit, and then exposed in accordance with a predetermined pattern in an aligner. Subsequently, the exposed semiconductor wafer is subjected to post-exposure bake processing and cooled in a cooling processing unit, and a developing solution is applied and the exposed pattern is developed in a developing unit. Finally, the semiconductor wafer is subjected to post-bake processing in the hot plate unit.
Out of such a series of processing steps, the steps except for exposure processing are performed by a resist coating and developing processing system into which the processing units are integrated. As one proposal for the structure of such a resist coating and developing processing system, there is proposed the structure in which a plurality of processing units for performing the processing are vertically stacked around a transfer path extending in a vertical direction, and the semiconductor wafer is carried into/out of each of the processing units by a main transfer machine which moves vertically in the transfer path and includes an arm moving in a horizontal direction. When a substrate is transferred between a plurality of processing units, such a processing system makes it possible to shorten the transfer route of the substrate and to downsize the system, and consequently the transfer of the substrate can be performed in a short time, thereby raising efficiency of the system.
In the processing system, however, the transfer of the substrate between the processing units is performed by the main transfer machine, and hence the entire processing speed is determined by the capacity of the main transfer machine. However, there is a limit to improvement in the capacity of the main transfer machine, and there is a possibility that the processing system can not sufficiently meet the recent increasing demands for improvement in throughput.
Compliance with these demands by an increase in the number of the main transfer machines is considered, but the system becomes complicated, thereby causing a rise in fabrication costs and complication of control.